Sepsis is an infection-initiated manifestation of the systemic inflammatory response syndrome that often progresses to septic shock, multiple organ failure with high risks of death. Sepsis is a particularly serious problem in the geriatric population, as the elderly patients with sepsis suffer much higher morbidity and mortality than younger patients. In fact, sepsis is a major cause of death in elderly patients at intensive care units in the US. Although this problem is increasingly recognized, the underlying mechanism(s) responsible for this age-associated vulnerability remain largely unknown. The long-term goal of our research is to determine the mechanisms responsible for the increased septic vulnerability in the aged, and to use this information to develop new treatment strategies for sepsis. The age-associated vulnerability to sepsis is also seen in animal models. We have shown that aged mice suffer significantly higher mortality than young mice in two commonly used models for sepsis; endotoxemia induced by bacterial lipopolysaccharide injection, and an intra-abdominal sepsis induced by cecal ligation and puncture. We have also found that the elevated mortality in aged mice is associated with altered inflammatory and coagulation responses, and increased oxidative damages. Our central hypothesis is that loss of homeostasis in old age leads to excessive inflammation, oxidative damage, and coagulation, contributing to the age-associated vulnerability to sepsis. Our objective in this project is to define the age-associated alterations in pathophysiology and gene expression in the mouse model of sepsis, and to develop strategies to improve the survival of the old mice with sepsis. To achieve these goals, we pursue the following three specific aims: (1) To determine the effects of aging on the pathophysiology of sepsis, (2) To identify the age-associated alterations in gene expression that affects mortality in sepsis, and (3) To test likely strategies for their ability to decrease age-associated mortality in sepsis. The information obtained from this project should provide the basis for new therapeutic strategies to substantially decrease the mortality in elderly patients with sepsis.